Author(s): Cauy Williams, Danielle Newbold
Mentor(s): Jacob Dean, Kim Weaver, Mackay Steffensen
Institution SUU
Photobilins, the photosynthetic pigments found in cyanobacteria and some algae, serve to carry out biological processes through light-generated energy transfer and transduction. Bilins are linear tetrapyrrole compounds that have two unique subunits characterized as a “dipyrrole” and “dipyrrinone.” This study focuses on N-methyl dipyrrinone (DPN), its methyl capped derivative, and a derivative 2-ethyl-1-methyl-3H,5H-dipyrrolo[1,2-c:2', 1'-Apyrimidine-3,5-dione (DPD), which covalently bridges the two pyrrole rings together. UV-vis absorption spectroscopy and fluorescence spectroscopy were used to extract key spectroscopic properties of these compounds including the molar extinction coefficient, the fluorescence quantum yield, and rate constants for radiative and nonradiative decay. In addition, we explored the photoreactivity of these molecules under constant illumination and in different pH conditions. We have found that the “unbridged” DPN compounds undergo rapid excited state decay while the pyrrole-bridged derivative does not, implicating the free torsion of pyrrole rings as the primary deactivation channel of these compounds.